-20 - 15 = -35
8/15 minus 7/20 is 11/60
5 - (-15) = 20
20 + 15 - 3 = 32
15/20 minus 6/20 which is 9/20 or 0.45
-10
1 and 19/20
5, as 20x0.75=15, so 20-15=5
15 + 6 - 1 = 20
Negative 15 plus positive 20 equals 20 minus 15, which equals 5.
Converting to twentieths, we get 8 over 20 minus 15 over 20, resulting in minus 7 over 20.
-20 -(-5) = -15 ie -(-5) = +5 therefore -20 +5 =15 (two double minuses = a positive)